Audio systems are systems used for processing audio signals. Usually the signal processing is performed by one or more modules that form an audio chain. When the system combines more than one module, it can be the case that the effect of a first module needs to be known by a subsequent module in the chain.
An example of such a system has a module that applies an attenuation factor to a signal, followed by another module that brings the signal back to full scale amplitude. Typically, the first module is a volume control module and the second one is an Automatic Gain Control (or AGC) module.
Although in the design of audio systems this configuration is not preferred, sometimes it cannot be avoided. There are cases in which separate modules are implemented in different hardware components. In this case there is no freedom to arrange the modules for the most preferred configuration. As a consequence a control mechanism is required to resolve the conflicts. This control mechanism retrieves information from certain modules and sends it to other modules.
In the above example, information corresponding to the gain change of the volume control module needs to be sent to the Automatic Gain Control (AGC) module so that this change is not counteracted by the AGC. This requires that the two modules communicate with each other by means of an external control mechanism.
When the audio system combines many modules, the required control mechanism can make the integration phase more complex.